1. Field of the Invention
This invention relates to an electrochemical storage cell or battery with at least one anode chamber filled with a molten alkali metal as the anolyte and at least one cathode chamber filled with a sulfur-containing catholyte substance, with the chambers separated from each other by an alkali-ion-conducting solid electrolyte, and to additives to improve the recharging capability of the electrochemical storage cell.
2. Description of the Prior Art.
An electrochemical storage cell or battery based on alkali metal and sulfur having at least one anode chamber and one cathode chamber separated from each other by an ion-conducting solid electrolyte, and a felt fabric of graphite or carbon contained in the cathode chamber in addition to the sulfur is known in the art as shown by German Published Prosecuted Application No. 1 671 760.
An important disadvantage of such cells is, however, that they can be only partially recharged with large currents. In an Na/S cell, for instance, this disadvantage is related to the fact that sulfur (with small percentages of dissolved Na.sub.2 S.sub.5) and Na.sub.2 S.sub.5 (with percentages of dissolved sulfur) form two immiscible liquids at the operating temperature of such a cell, which is between 300.degree. and 350.degree. C. For, if a discharged Na/S cell which contains Na.sub.2 S.sub.3 in the cathode chamber, is recharged, then sulfides richer in sulfur are formed first until Na.sub.2 S.sub.5 has been produced in the entire cathode chamber or at least locally. Upon further charging, liquid sulfur is then produced at the points with a high electrochemical reaction rate. The sulfur being an insulator, blocks the electrochemical processes at these points.
In storage cells with high current densities, such as are presently planned for covering peak loads in electrical networks, particularly in connection with nuclear reactors, recharging as rapidly and completely as possible is especially important.